pci: Add Linux sysfs implementation of HW.PCI.Dev

In Linux' sysfs, each PCI device has a directory like:

    /sys/devices/pci0000:00/0000:00:02.0/

Therein, the file `config` represents the PCI device's configuration
space. Alas, it's not mappable so we work on a read only copy. Should
we ever need dynamic read/write access, we'd have to implement it
using read()/write().

IO and MMIO resources are represented by mappable files, `resource[0-5]`
for uncacheable accesses and `resource[0-5]_wc` for write-combining
access.

Change-Id: I1358e9336edaf75e8eff50808a8169b997817d7e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/20554
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
7 files changed